Hypophosphatemia induced by mechanical ventilation in patients with chronic obstructive pulmonary disease.

The aim of this study was to assess prospectively the variations of serum phosphorus concentration (P) after onset of mechanical ventilation (MV) in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory acidosis. In 14 COPD patients, we measured P, PaCO2, and pH, immediately before MV (H0), then one hour (H1), 4 (H4), 7 (H7), 12 (H12), and 24 h (H24) after starting MV. P at H0 was in or above the normal range in ten patients and below normal range in four patients. P decreased significantly (p less than .001) after MV at H1, H4, H7, H12, and H24. Hypophosphatemia was present in all patients after MV, but was severe (p less than .3 mmol/L) in only two patients. There was a significant correlation (r = .56 p less than .01) between the decrease of P and the increase of pH after MV. Hypophosphatemia was a constant and early finding after institution of MV in COPD patients and was presumably related to an intracellular shift of P secondary to the correction of respiratory acidosis.